Method of forming on-chip decoupling capacitor with bottom electrode layer having surface roughness

Abstract

On-chip decoupling capacitor structures, and methods of fabricating such decoupling capacitors are disclosed. On-chip decoupling capacitors help to reduce or prevent L di/dt voltage droop on the power grid for high surge current conditions. The inclusion of one or more decoupling capacitors on a chip, in close proximity to the power grid conductors reduces parasitic inductance and thereby provides improved decoupling performance with respect to high frequency noise. In one embodiment of the present invention, a capacitor stack structure is inserted between metal interconnect layers. Such a capacitor stack may consist of a bottom electrode/barrier; a thin dielectric material having a high dielectric constant; and a top electrode/barrier. In an alternative embodiment, the bottom electrode and/or bottom metal interconnect layer have three dimensional texture to increase the surface area of the capacitor. An illustrative method embodying the present invention, includes fabricating the on-chip decoupling capacitor stack structure and electrically connecting the capacitor to provide efficient capacitive de-coupling. In order to facilitate the removal of photoresist by an oxygen plasma process prior to exposing copper conductors during the capacitor stack etch, an Al hardmask can be used to protect the capacitor formed with Ta 2 O 5 dielectric, or a W hardmask can be used to protect the capacitor formed with BST dielectric.

1. A method comprising:
 forming an interlayer dielectric (ILD); 
 forming a first conductor structure in said ILD; 
 forming a bottom electrode layer over said first conductor structure from two or more layers of different materials, said bottom electrode layer having a surface including a series of grooves, said bottom electrode layer including conductive material that prevents diffusion of copper and oxygen, wherein the formation of the bottom electrode layer having said surface including said series of grooves comprises depositing a polycrystalline film of said conductive material on said first conductor structure, and selectively etching grain boundaries of said polycrystalline film with a wet chemical etch; 
 forming a dielectric layer over said bottom electrode layer in an oxidizing atmosphere; 
 forming a top electrode layer over said dielectric layer from two or more layers of different materials, said top electrode layer including conductive material that prevents diffusion of copper and oxygen; and 
 forming a hard mask over said top electrode layer, said hard mask comprising tungsten. 
 
     
     
       2. The method of  claim 1 , further comprising:
 forming a photoresist layer over said hard mask; 
 patterning said photoresist layer to expose a portion of said hard mask; 
 etching through said exposed portion of said hard mask, as well as said top electrode layer, said dielectric layer, and said bottom electrode layer under said exposed portion of said hard mask; 
 stripping said photoresist layer; 
 forming an etch stop layer over exposed surfaces of said ILD, said bottom electrode layer, said dielectric layer, said top electrode layer, and said hard mask; 
 forming a second ILD over said etch stop layer; and 
 forming a second conductor structure in said second ILD. 
 
     
     
       3. The method of  claim 1  wherein said dielectric layer has a dielectric constant greater than that of silicon dioxide. 
     
     
       4. The method of  claim 1  wherein said top electrode layer comprises: TaN, TiN, or WN. 
     
     
       5. The method of  claim 1  wherein said top electrode layer comprises: Pt, Ir, or Ru. 
     
     
       6. The method of  claim 1  wherein at least one of said ILD and said second ILD comprises silicon dioxide. 
     
     
       7. The method of  claim 1  wherein at least one of said ILD and said second ILD comprises fluorine doped oxides of silicon. 
     
     
       8. The method of  claim 1  wherein at least one of said ILD and said second ILD comprises carbon doped oxides of silicon. 
     
     
       9. The method of  claim 1  wherein at least one of said ILD and said second ILD comprises porous oxides of silicon. 
     
     
       10. The method of  claim 1  wherein at least one of said ILD and said second ILD comprises organic polymers. 
     
     
       11. A method comprising:
 forming an interlayer dielectric (ILD); 
 forming a first conductor structure in said ILD; 
 forming a bottom electrode layer over said first conductor structure from two or more layers of different materials, said bottom electrode layer having a surface including a series of grooves, said bottom electrode layer including conductive material that prevents diffusion of copper and oxygen, wherein the formation of the bottom electrode layer having said surface including said series of grooves comprises depositing a film of said conductive material with columnar grains over said first conductor structure, and selectively etching boundaries of said columnar grains; 
 forming a dielectric layer over said bottom electrode layer in an oxidizing atmosphere; 
 forming a top electrode layer over said dielectric layer from two or more layers of different materials, said top electrode layer including conductive material that prevents diffusion of copper and oxygen; and 
 forming a hard mask over said top electrode layer, said hard mask comprising tungsten. 
 
     
     
       12. The method of  claim 11 , further comprising:
 forming a photoresist layer over said hard mask; 
 patterning said photoresist layer to expose a portion of said hard mask; 
 etching through said exposed portion of said hard mask, as well as said top electrode layer, said dielectric layer, and said bottom electrode layer under said exposed portion of said hard mask; 
 stripping said photoresist layer; 
 forming an etch stop layer over exposed surfaces of said ILD, said bottom electrode layer, said dielectric layer, said top electrode layer, and said hard mask; 
 forming a second ILD over said etch stop layer; and 
 forming a second conductor structure in said second ILD. 
 
     
     
       13. The method of  claim 11  wherein said dielectric layer has a dielectric constant greater than that of silicon dioxide. 
     
     
       14. The method of  claim 11  wherein said top electrode layer comprises: TaN, TiN, or WN. 
     
     
       15. The method of  claim 11  wherein said top electrode layer comprises: Pt, Ir, or Ru. 
     
     
       16. The method of  claim 11  wherein at least one of said ILD and said second ILD comprises silicon dioxide. 
     
     
       17. The method of  claim 11  wherein at least one of said ILD and said second ILD comprises fluorine doped oxides of silicon. 
     
     
       18. The method of  claim 11  wherein at least one of said ILD and said second ILD comprises carbon doped oxides of silicon. 
     
     
       19. The method of  claim 11  wherein at least one of said ILD and said second ILD comprises porous oxides of silicon. 
     
     
       20. The method of  claim 11  wherein at least one of said ILD and said second ILD comprises organic polymers.